A formed product which is formed by superimposing flat portions of an elongated metal plate by roll forming such that the flat portions are aligned in the widthwise direction, and uniting the superimposed portions together by welding is disclosed, for example, in Japanese Patent Application Laid-Open (kokai) No H8-104139 (Patent Document 1). In this formed product, the portions superimposed through roll forming are welded together along a line by seam welding or laser welding.